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Culturally, the reef has been a rich part of
the landscape for Aboriginal and Torres Strait
Islander peoples, who have canoed it and shed
it and shared myths about its creatures for gen-
erations. But historians aren't sure how deep
their knowledge went of the reef 's geology and
animal life. A few decades a er Cook's run-in
with the behemoth beneath the sea, English
cartographer Matthew Flinders---who also had
a mishap or two while "threading the needle"
among the reefs---gave the entity its name,
inspired by its size. All told, if the reef 's main
chunks were plucked from the sea and laid out
to dry, the rock could cover all of New Jersey,
with coral to spare.
EXPANSION AND EROSION is mam-
moth reef owes its existence to organisms typi-
cally no bigger than a grain of rice. Coral polyps,
the reef 's building blocks, are tiny colonial ani-
mals that house symbiotic algae in their cells.
As those algae photosynthesize---using light to
create energy---each polyp is fueled to secrete a
"house" of calcium carbonate, or limestone. As
one house tops another, the colony expands like
a city; other marine life quickly grabs on and
spreads, helping cement all the pieces together.
O Australia's eastern edge, conditions are
ripe for this building of stone walls. Corals grow
best in shallow, clear, turbulent water with lots
of light to support photosynthesis. Millions of
polyp generations later, the reef stands not as
a singular thing but as a jumble whose shapes,
sizes, and life-forms are determined by where
in the ocean they lie---how close to shore, for
example---and what forces work on them, such
as heavy waves. Go far enough from the coast,
where the light is low and the waters are deeper,
and there's no reef at all.
"In the Great Barrier Reef, corals set the pat-
terns of life from end to end," says Charlie Ve-
ron, coral expert and a longtime chief scientist
for the Australian Institute of Marine Science.
With over 400 species in the region, "they struc-
ture the entire environment; they're the habitat
for everything else here." e perfect tempera-
ture, clarity, and currents enable plate corals,
for example, to increase in diameter up to a foot
IF THE REEF'S MAIN CHUNKS WERE
PLUCKED FROM THE SEA AND LAID OUT
TO DRY, THE ROCK COULD COVER
ALL OF NEW JERSEY,
WITH CORAL TO SPARE.
Cardinal sh zip by a hawksbill
turtle as it rests among feathery
invertebrates called hydroids.
Illegally harvested for their
shells, hawksbills are declining
globally. Some 3,000 nest along
the northern Barrier Reef.
ERETMOCHELYS IMBRICATA TURTLE ;
APOGON LEPTOFASCIATUS FISH ;
LYTOCARPUS SP. HYDROID
David Doubilet divided his time between the Great
Barrier Reef 's remote north and its touristed south
and central areas. Jennifer S. Holland is a sta writer.